4-Nitrophenol reduction and antibacterial activity of Ag-doped TiO₂ photocatalysts

Water contamination by organic pollutants is a serious environmental problem. 4-Nitrophenol (4-NP) is a potentially harmful chemical, which is commonly present in industrial effluents and can severely damage human health. Photocatalytic reduction of hazardous 4-NP by nano-sized materials to produce 4-aminophenol (4-AP), which is a commercially valuable product, is a promising alternative as the process is framed within the circular economy. In this context, Ag-doped TiO₂ (AT) catalysts were synthesized by liquid impregnation and reduction techniques, and their structure, morphology, elemental composition, textural, and light absorption properties were evaluated by XRD, Raman spectroscopy, SEM, TEM, EDS, BET, and DRS spectroscopy. AT catalysts exhibited an enhanced photocatalytic reduction of 4-NP into 4-aminophenol (4-AP) in the presence of NaBH₄. Among the tested catalysts, AT21 prepared by a simple aqueous reduction method showed the highest activity reaching about 98% 4-NP reduction within 10 min. Antibacterial tests of these catalysts against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa revealed that AT21 also exhibited the lowest minimum inhibitory concentration, suggesting that it has the strongest antibacterial activity. These findings suggest that AT21 catalyst with improved catalytic and antibacterial properties can potentially be utilized for the remediation of 4-NP-contaminated water environment.